There are many settings wherein it is desirable to attach test equipment (e.g., a voltmeter or an oscilloscope) to one or more pins of an integrated circuit. These settings include the laboratory, the production floor, and the maintenance shop. A variety of "DIP clips" have been produced to facilitate this for the venerable dual in-line package. More recent packaging styles having a high number of closely spaced pins on all four sides of the IC's package have made it nearly imperative that all but the most casual (or the most desperate?) probing be performed with the aid of some special tool. This is because it is difficult to locate or identify a particular pin or pins out the many, and because it is physically difficult to maintain proper contact with the probe tip. The legs or pins of the larger IC's are quite small and close together; a slip of the hand can result in a short circuit either between adjacent pins or between a pin of the IC and a nearby component. What's more, this type of unassisted probing, while seemingly quick and flexible, uses up a hand that might better be used doing something else. There is also the issue of how to establish longer term probe contact where the probe is left in place for anywhere from a few minutes to an hour or so.
Accordingly, there has been considerable interest of late in strategies for connecting test equipment to the newer styles of integrated circuit packages. It is in this context that the above incorporated patents to Wardwell arose. The wedge connection strategy that is disclosed therein is truly an improvement over the conventional technique of gripping (squeezing) the IC between opposing contacts disposed on opposite sides of the IC, such as is done with the old fashioned DIP clip. Wardwell's wedges take an entirely different approach, as summarized by the next four paragraphs (as revised after being robbed from the incorporated Wardwell patents).
The (Wardwell) wedge connector comprises tapered fingers of conductive metal separated by an insulator. The tapered fingers are wedge-shaped, in that they are thinnest at their tips, so that they may more easily enter the space between adjacent legs of an IC. A row of tapered wedges (i.e., tapered fingers) is assembled, and spaced apart to interdigitate with the legs of the IC. That is, the legs of the IC also form a row with an amount of inter-leg spacing between the legs along the direction of the row. The IC legs have sides that face each other along the direction of the row, and that are separated by the amount of the inter-leg spacing. By interdigitation we mean that the tapered fingers or wedges penetrate into the inter-leg space and contact the facing sides of the IC legs. Thus, the left-hand side of a wedge entering a particular inter-leg space will come into electrical contact with the right-hand side of the IC leg on the left of that inter-leg space, and the right-hand side of that wedge will come into electrical contact with left-hand side of the IC leg on the right of that inter-leg space. As the depth of penetration is increased the thicker parts of the wedge enter the inter-leg space, filling it completely and causing good wiping action and firm contact pressure between the sides of the IC legs and the sides of the wedges.
Within the row of wedges, the left-hand side of each wedge is electrically connected to the right-hand side of its neighboring wedge on the right, which, by implication means that the right-hand side of each wedge is also electrically connected to the left-hand side of its neighboring wedge to the right. This interconnectedness of the wedges in a row thereof produces a very desirable effect: if there are n-many legs on the IC and n+1 wedges in a row, then each leg of the IC is in electrical contact at two different places with two different wedges. This adds a robust reliability to the wedge connector.
It is to be noted that the wedges interdigitate with the facing sides of adjacent legs of the IC, and that no attempt is made to produce contact with the outer faces of the legs of the IC; instead, the wedges pass between the legs.
Wedge compliance can be improved by fabricating the wedges with air gaps between those portions of their internal layers of material that correspond to the tapered portions of the wedge. This makes the wedges more compressible over their tapered region, as well as somewhat more bendable in the side-to-side direction. Correct initial interdigitation is enhanced by beveling the ends of the conductive surfaces at the tips of the wedges. This reduces the cross section of the wedges, making them "sharper" so that they more easily engage the empty inter-leg spaces. Solder debris accumulation is reduced by having a center piece of insulating material at the central core of the wedge extend beyond the tapered end of the wedge by a small amount, say ten thousandths of an inch. The beveling of the conductive sides of the tapered wedges also assists with solder debris abatement, as sharper edges present less of a shelf with which to gouge the solder and carry a build-up of scraped off solder debris.
However, the various wedge contact apparatus disclosed in the incorporated patents to Wardwell, and summarized above, are all oriented around making simultaneous contact with, if not each and every pin on the IC, at least a large number of pins, and, if not from all four sides of a quad flat pack, at least from two different sides. There are many instances where the task at hand requires probing only one or a relatively few number of pins at a time. The strategy of wedging between the pins or legs of an IC to obtain electrical contact is an attractive one for many reasons, most of which are set out in Wardwell's patents. It would be desirable if the wedge probe technique could be adapted to making simultaneous contact (for probing) with one, two, or some other small number of adjacent pins or legs of an IC, and for readily changing the location on the IC of where such simultaneous contact occurred, almost as readily as one deploys a scope probe on a low density printed circuit board loaded with discrete parts. That is, it would be desirable if a wedge probe for electrically connecting to just one or to a limited and relatively small number of pins on an IC were "portable", in the sense that it is readily re-deployable at different locations on the IC. Such a wedge probe would have far fewer wedges than needed to simultaneously connect to every pin on the IC, and would allow an easy perusal of the IC's signals by simply repositioning the probe. Such a portable wedge probe would also be less expensive than its full sized counterpart.